The present invention is in the general field of animal feeding and relates particularly to the feeding of ruminant animals, especially sheep.
With the continuing growth of world population, it is increasingly important that effective means be found for increasing the food supply. One means of doing this is to increase the production of the animals which are a major source of human nutritional needs. Ruminant animals comprise a substantial part of the total food stock.
One serious problem with raising ruminant animals, particularly sheep, is the formation of kidney or bladder stones in the animals. Excessive formation of such stones causes premature death of affected animals.
Urinary stones are also found in fairly high incidence in domestic animals such as cats and dogs. The problem is especially severe in male cats that have been neutered. The stones not only cause great pain or even death to the affected animal, and mental pain and anguish to their owners, they also create financial burdens for the latter. In addition to expenses for medical treatments, more expensive and carefully selected pet foods must be fed to the animal susceptible to stones in the urinary tract. It has been unexpectedly discovered that the addition of a small amount of zeolite, such as a zeolite A, to the animals regular feed will effectively reduce or inhibit the formation of such stones or urinary calculi.
Zeolites are crystalline, hydrated aluminosilicates of alkali and alkaline earth cations, having infinite, three-dimensional structures.
Zeolites consist basically of a three-dimensional framework of SiO.sub.4 and AlO.sub.4 tetrahedra. The tetrahedra are crosslinked by the sharing of oxygen atoms so that the ratio of oxygen atoms to the total of the aluminum and silicon atoms is equal to two or 0/(Al+Si)=2. The electrovalence of each tetrahedra containing aluminum is balanced by the inclusion in the crystal of a cation, for example, a sodium ion. This balance may be expressed by the formula Al/Na=1. The spaces between the tetrahedra are occupied by water molecules prior to dehydration.
Zeolites A may be distinguished from other zeolites and silicates on the basis of their composition and X-ray powder diffraction patterns and certain physical characteristics. The X-ray patterns for these zeolites are described below. The composition and density are among the characteristics which have been found to be important in identifying these zeolites.
The basic formula for all crystalline sodium zeolites may be represented as follows: EQU Na.sub.2 O.Al.sub.2 O.sub.3.xSiO.sub.2.yH.sub.2 O.
In general, a particular crystalline zeolite will have values for "x" and "y" that fall in a definite range. The value "x" for a particular zeolite will vary somewhat since the aluminum atoms and the silicon atoms occupy essentially equivalent positions in the lattice. Minor variations in the relative number of these atoms do not significantly alter the crystal structure or physical properties of the zeolite. For zeolite A, the "x" value normally falls within the range 1.85.+-.0.5.
The value for "y" is not necessarily an invariant for all samples of zeolites. This is true because various exchangeable ions are of different size, and, since there is no major change in the crystal lattice dimensions upon ion exchange, the space available in the pores of the zeolite to accommodate water molecules varies.
The average value for "y" for zeolite A is 5.1. The formula for zeolite A may be written as follows: EQU 1.0.+-.0.2Na.sub.2 O.Al.sub.2 O.sub.3.1.85.+-.0.5SiO.sub.2.yH.sub.2 O.
In the formula, "y" may be any value up to 6.
An ideal zeolite A has the following formula: EQU (NaAlSiO.sub.4).sub.12.27H.sub.2 O
Among the ways of identifying zeolites and distinguishing them from other zeolites and other crystalline substances, the X-ray powder diffraction pattern has been found to be a useful tool. In obtaining the X-ray powder diffraction patterns, standard techniques are employed. The radiation is the K.alpha. doublet of copper and a Geiger counter spectrometer with a strip chart pen recorder is used. The peak heights, I, and the positions as a function of 2.theta. where .theta. is the Bragg angle, are read from a spectrometer chart. From these, the relative intensities, 100 I/I.sub.o, where I.sub.o is the intensity of the strongest line or peak and d the interplanar spacing in angstroms corresponding to the recorded lines are calculated.
X-ray powder diffraction data for a sodium zeolite A are given in Table I.
TABLE I ______________________________________ X-RAY DIFFRACTION PATTERN FOR ZEOLITE A 100 I h.sup.2 + k.sup.2 + l.sup.2 d (.ANG.) I.sub.o ______________________________________ 1 12.29 100 2 8.71 70 3 7.11 35 4 6.15 2 5 5.51 25 6 5.03 2 8 4.36 6 9 4.107 35 10 3.895 2 11 3.714 50 13 3.417 16 14 3.293 45 16 3.078 2 17 2.987 55 18 2.904 10 20 2.754 12 21 2.688 4 22 2.626 20 24 2.515 6 25 2.464 4 26 2.414 &gt;1 27 2.371 3 29 2.289 1 30 2.249 3 32 2.177 7 33 2.144 10 34 2.113 3 35 2.083 4 36 2.053 9 41 1.924 7 42 1.901 4 44 2.858 2 45 1.837 3 49 1.759 2 50 1.743 13 53 1.692 6 54 1.676 2 55 1.661 2 57 1.632 4 59 1.604 6 ______________________________________
The more significant d values for zeolite A are given in Table II.
TABLE II ______________________________________ MOST SIGNIFICANT d VALUES FOR ZEOLITE A d Value of Reflection in A ______________________________________ 12.2 .+-. 0.2 8.7 .+-. 0.2 7.10 .+-. 0.15 5.50 .+-. 0.10 4.10 .+-. 0.10 3.70 .+-. 0.07 3.40 .+-. 0.06 3.29 .+-. 0.05 2.98 .+-. 0.05 2.62 .+-. 0.05 ______________________________________
Occasionally, additional lines not belonging to the pattern for the zeolite appear in a pattern along with the X-ray lines characteristic of that zeolite. This is an indication that one or more additional crystalline materials are mixed with the zeolite in the sample being tested. Small changes in line positions may also occur under these conditions. Such changes in no way hinder the identification of the X-ray patterns as belonging to the zeolite.
The particular X-ray technique and/or apparatus employed, the humidity, the temperature, the orientation of the powder crystals and other variables, all of which are well known and understood to those skilled in the art of X-ray crystallography or diffraction can cause some variations in the intensities and positions of the lines. These changes, even in those few instances where they become large, pose no problem to the skilled X-ray crystallographer in establishing identities. Thus, the X-ray data given herein to identify the lattice for a zeolite, are not to exclude those materials which, due to some variable mentioned or otherwise known to those skilled in the art, fail to show all of the lines, or show a few extra ones that are permissible in the cubic system of that zeolite, or show a slight shift in position of the lines, so as to give a slightly larger or smaller lattice parameter.
A simpler test described in "American Mineralogist," Vol. 28, page 545, 1943, permits a quick check of the silicon to aluminum ratio of the zeolite. According to the description of the test, zeolite minerals with a three-dimensional network that contains aluminum and silicon atoms in an atomic ratio of Al/Si=2/3=0.67, or greater, produce a gel when treated with hydrochloric acid. Zeolites having smaller aluminum to silicon ratios disintegrate in the presence of hydrochloric acid and precipitate silica. These tests were developed with natural zeolites and may vary slightly when applied to synthetic types.
U.S. Pat. No. 2,882,243 describes a process for making zeolite A comprising preparing a sodium-aluminum-silicate water mixture having an SiO.sub.2 :Al.sub.2 O.sub.3 mole ratio of from 0.5:1 to 1.5:1, and Na.sub.2 O/SiO.sub.2 mole ratio of from 0.8:1 to 3:1, and an H.sub.2 O/Na.sub.2 O mole ratio of from 35:1 to 200:1, maintaining the mixture at a temperature of from 20.degree. C. to 175.degree. C. until zeolite A is formed, and separating the zeolite A from the mother liquor.
It is therefore a principal object of the present invention to provide a feed formulation for more effective use of zeolites, especially zeolite A in animal feeds or in an animal's diet, particularly in the diets of ruminant animals, especially sheep.
It is an important object of the present invention to provide an improved feed formulation for animals which contains a small amount of zeolite A.
It is another object of the invention to provide an animal feed containing zeolite A which effectively inhibits the formation of kidney stones or urinary calculi in animals.
Still another object of the invention is to cost effectively increase the production of animals slaughtered for food.
Yet a further object of the present invention is to provide an improve feed formulation for domestic animals such as cats and dogs which effectively inhibits the formation of kidney stones or urinary calculi in the domestic animal.
Other objects and advantages of the invention will be more fully understood from a reading of the description and claims hereinafter.